How does using a return clause before a recursive function call differ from not using one?

Question

I was just experimenting with some recursion and noticed something that confused me. Let me illustrate with some code examples:

function loop(x) {
  if (x >=          


        

Answer 1

If you don't return from a Javascript function there is an implicit "return undefined" in the end.

function loop(x) {
  if (x >= 10)
    return x;
  loop(x + 1); // the recursive call
  return undefined;
}

As you can see, te recursive call is being called and having its return value ignored. This is just like what happens when you call a function like console.log - the function gets called and runs any side-effects but you discard the return value in the end.